During this fellowship I will be able to enhance my understanding in characterization of antiphospholipid antibodies and their role in causation of recurrent thrombosis and pregnancy loss. The lupus anticoagulant was believed to be a phospholipid binding antibody which induced thrombosis by affecting phospholipid interactions with clotting proteins. But recent data is suggesting that these antibodies may bind prothrombin, or the apo-lipoprotein, beta 2 glucoprotein 1. and that (S) how the former hypothesis is under the question mark. The research goals under this fellowship will be to determinate the specificity of immunoglobulins with lupus anticoagulant activity by studying their action on the prothrombinase complex, to compare the effects of whole IgG and ACA on the prothrombinase complex and to determine the effect of beta 2 glycoprotein 1 on lupus anticoagulant activity.